Entrained-Flow GasifierThe EERC's pilot-scale entrained-flow gasifier (EFG) has been used for various carbonaceous feeds ranging in quality from lignite to petcoke. Syngas has been generated for various applications, including Fischer–Tropsch catalyst testing, pyrolysis, examination of slag formation, hydrogen production, and more. Because of the high temperatures employed in EFG operation, very little tar or hydrocarbon is generated, and the product gas has been successfully cleaned to nondetectable limits of contaminants such as H2S and particulate.
Pulverized coal particles fed into the EFG reach slagging temperatures in a residence time of a few seconds. The EFG is downfired and housed in a high-pressure vessel approximately 24 in. in diameter and 7 ft in length. It fires 4 to 10 lb/hr of coal and produces up to 10 scfm of syngas. This reactor has the capability to run in either oxygen- or simulated air-blown mode by blending air with nitrogen. The multizone heating system is capable of producing syngas at temperatures up to 1500°C (2700°F). Refractory is used as insulation to help maintain the required temperature in the furnace. This refractory has the ability to withstand high temperatures while retaining its insulating properties at high pressure. A water-cooled jacket surrounds the outside of the vessel and is used to remove any excess heat escaping through the refractory.
The pressure inside the vessel can range up to 300 psig and is balanced with a 300-psi atmosphere outside the reactor zone alumina tube. Water, nitrogen, or syngas quench at the bottom of the furnace causing slag to solidify and drop into a refractory-lined slag trap as syngas passes 90° through a horizontal tee.
Pulverized coal is fed to the furnace using a K-Tron® loss-in-weight feeder that provides online measurement of coal feed rate. Coal exits the feeder via a twin-screw feed motor contained in a pressurized vessel. The design allows for 4 hours of continuous feed use at 8 lb/hr before the coal hopper needs to be refilled through a cycling lock hopper. The system may also be fed using coal–water slurry. Pneumatic transport gases consisting of nitrogen or recycled syngas are used to carry the pulverized coal into the reaction zone. Syngas produced by the EFG passes through subsequent pollution control devices, including a transport desulfurization reactor, hot-gas filter vessel, fixed-bed sorbents and shift catalysts, and water-cooled quench pots. A syngas compressor enables recycle capability to increase gas velocity while reducing nitrogen dilution. The feeder and back-end pollution control devices are shared with the EERC's fluid-bed gasifier and allow flexibility in operation without requiring excessive maintenance or capital cost for testing.